Piston type compressor

ABSTRACT

In a piston type compressor, a housing includes a cylinder block that forms plural cylinder bores and an accommodating hole at a center thereof. The valve port assembly connected to the cylinder block includes suction and discharge ports, suction and discharge valves made of flapper valves. An end portion of the drive shaft rotatably supported by the housing is slidably accommodated in the accommodating hole. The piston in each cylinder bore and the valve port assembly form a compression chamber. The cylinder block forms therein communication holes that connect each compression chamber to the end portion that forms therein a residual gas bypass passage. The residual gas bypass passage connects one communication hole, which communicates with the high-pressure side compression chamber that has finished discharge process of gas, to another communication hole, which communicates with the compression chamber that is lower in pressure than the high-pressure side compression chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a piston type compressor that is, for example, used for a vehicle air conditioner.

Such a piston type compressor is disclosed on pages 3 and 4, and FIG. 1 of Unexamined Japanese Patent Publication No. 10-47241. A cylinder block forms therein a plurality of cylinder bores that surround a drive shaft. Each cylinder bore accommodates therein a piston and defines therein a compression chamber by the piston and a valve port assembly. The valve port assembly is provided with suction ports, suction valves made of flapper valves, discharge ports, and discharge valves made of flapper valves. As the piston reciprocates, refrigerant gas is introduced into the compression chamber through the suction port by pushing away the suction valve, and is compressed in the compression chamber, and is discharged from the compression chamber through the discharge port by pushing away the discharge valve.

In the piston type compressor, the piston at a top dead center is spaced at a clearance from the valve port assembly such that the piston at the top dead center does not collide with the valve port assembly. Additionally, the discharge ports, which are formed in the valve port assembly, are constantly in communication with the corresponding compression chambers. That is, even if the piston is positioned at the top dead center, the compression chamber still has its slight volume.

Accordingly, even in a state where the piston is positioned at the top dead center, high-pressure refrigerant gas still remains in the compression chamber, which is called residual gas. Then, the residual gas in the compression chamber expands in a suction cycle where the piston moves from the top dead center to the bottom dead center, and new refrigerant gas is prevented from introduced into the compression chamber through the suction port and the suction valve during the expansion of the residual gas. As a result, the amount of refrigerant gas introduced into the compression chamber is smaller by the increase of the residual gas due to the expansion, with the result of deteriorated efficiency of the refrigerant gas introduced into the compression chamber. Therefore, there has been a need for a piston type compressor that has a high efficiency of gas introduced into the compression chamber.

SUMMARY OF THE INVENTION

In accordance with the present invention, a piston type compressor has a housing, a drive shaft, a valve port assembly and a piston. The housing includes a cylinder block that forms a plurality of cylinder bores and an accommodating hole at a center of the cylinder block. The valve port assembly is connected to the cylinder block. The valve port assembly includes suction ports, suction valves made of flapper valves, discharge ports, and discharge valves made of flapper valves. The drive shaft is rotatably supported by the housing. An end portion of the drive shaft is slidably accommodated in the accommodating hole. The piston is accommodated in each of the cylinder bores. The piston and the valve port assembly form a compression chamber. The cylinder block forms therein communication holes that connect each of the compression chambers to the end portion of the drive shaft. The end portion of the drive shaft forms therein a residual gas bypass passage. The residual gas bypass passage connects one communication hole, which communicates with the compression chamber on a high-pressure side that has finished discharge process of gas, to another communication hole, which communicates with the compression chamber that is lower in pressure than the high-pressure side compression chamber. As the piston reciprocates, gas is introduced into the compression chamber through the suction port by pushing away the suction valve, compressed in the compression chamber and discharged from the compression chamber through the discharge port by pushing away the discharge valve.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a piston type compressor according to a first preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view that is taken along the line I-I in FIG. 1;

FIG. 3 is a linearly expanded plan view illustrating the rotational motion of the rear end portion of a drive shaft according to the first preferred embodiment of the present invention;

FIG. 4 is a cross-sectional view of a drive shaft near the rear end portion of another piston type compressor according to a second preferred embodiment of the present invention;

FIG. 5 is a cross-sectional view of a drive shaft near the rear end portion of another piston type compressor according to a third preferred embodiment of the present invention; and

FIG. 6 is a linearly expanded plan view illustrating the rotational motion of the rear end portion of a drive shaft according to the third preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of a variable displacement piston type compressor 10, which is a part of a refrigerant circuit of a vehicle air conditioner, according to the present invention will now be described with reference to FIGS. 1 through 3.

FIG. 1 illustrates a longitudinal cross-sectional view of the compressor 10. The front side and the rear side of the compressor 10 correspond to the left side and the right side of FIG. 1, respectively. As shown in FIG. 1, the housing of the compressor 10 includes a cylinder block 11, a front housing 12 fixedly connected to the front end of the cylinder block 11, and a rear housing 14 fixedly connected to the rear end of the cylinder block 11.

The compressor 10 also includes a valve port assembly 13, which is interposed between the cylinder block 11 and the rear housing 14. The valve port assembly 13 is formed by layering a suction valve plate 13 a, a valve port plate 13 b, a discharge valve plate 13 c and a retainer plate 13 d, in this order from the side of the cylinder block 11.

The housing forms therein a crank chamber 16 between the cylinder block 11 and the front housing 12. A drive shaft 17 is rotatably supported between the cylinder block 11 and the front housing 12 so as to extend through the crank chamber 16. The drive shaft 17 is supported by the front housing 12 through a radial bearing 18 at its front-end portion. The supporting structure of the other end (a rear end portion 38) of the drive shaft 17 will be described later. The drive shaft 17 is driven by a vehicle engine (not shown).

In the crank chamber 16, a lug plate 22 is secured to the drive shaft 17 so as to rotate integrally therewith. In the crank chamber 16, a thrust bearing 19 is interposed between the inner wall surface of the front housing 12 and the lug plate 22. The crank chamber 16 accommodates therein a swash plate 23, which is slidably and inclinably supported by the drive shaft 17. A hinge mechanism 24 is interposed between the lug plate 22 and the swash plate 23. The swash plate 23 is connected to the lug plate 22 through the hinge mechanism 24 and supported by the drive shaft 17 thereby synchronously rotate with the lug plate 22 and the drive shaft 17, while it is inclinable to the drive shaft 17 with a slide movement in the direction along the axis L of the drive shaft 17.

The cylinder block 11 forms therein a plurality (six in the first preferred embodiment, two of which are shown in FIG. 1) of cylinder bores 25, which are located at equiangular positions to surround the rear end portion 38 of the drive shaft 17. Each cylinder bore 25 accommodates therein a single-headed piston 26 so as to reciprocate. The front and rear openings of the cylinder bore 25 are respectively closed by the front end surface of the valve port assembly 13 (strictly, the suction valve plate 13 a) and the top end surface of the piston 26, thereby forming a compression chamber 27 between the piston 26 and the valve port assembly 13 (strictly, the suction valve plate 13 a). The piston 26 engages the outer periphery of the swash plate 23 through a pair of shoes 28. Accordingly, as the swash plate 23 rotates with the rotation of the drive shaft 17, the swash plate 23 is oscillated frontward and rearward in the direction of the axis L of the drive shaft 17. The oscillation of the swash plate 23 reciprocates the piston 26 frontward and rearward along the axis L.

The housing forms therein a suction chamber 29 and a discharge chamber 30 between the valve port assembly 13 and the rear housing 14. The valve port assembly 13 forms therein suction ports 31 in the valve port plate 13 b and suction valves 32 made of flapper valves in the suction valve plate 13 a between the suction chamber 29 and the compression chambers 27. The valve port assembly 13 forms therein discharge ports 33 in the valve port plate 13 b and discharge valves 34 made of flapper valves in the discharge valve plate 13 c between the discharge chamber 30 and the compression chambers 27. The retainer plate 13 d is formed to regulate the maximum opening degree of the discharge valves 34.

Refrigerant gas in the suction chamber 29 is introduced into the compression chamber 27 through the suction port 31 as the piston 26 moves from the top dead center to the bottom dead center to decrease the pressure in the compression chamber 27 and open the suction valve 32. The refrigerant gas introduced in the compression chamber 27 is compressed up to a predetermined pressure value as the piston 26 moves from the bottom dead center to the top dead center. After that the compressed refrigerant gas is discharged to the discharge chamber 30 through the discharge port 33 by the opening of the discharge valve 34. Compression reactive force applied to the pistons 26 is received by the thrust bearing 19 through the swash plate 23, the hinge mechanism 24 and the lug plate 22.

The housing of the compressor 10 includes a bleed passage 35, a supply passage 36 and a control valve 37. The bleed passage 35 connects the crank chamber 16 to the suction chamber 29. The supply passage 36 connects the discharge chamber 30 to the crank chamber 16. The control valve 37 is located in the supply passage 36. The regulation of the opening degree of the control valve 37 controls the balance between the amount of high-pressure discharged gas into the crank chamber 16 through the supply passage 36 and the amount of gas from the crank chamber 16 through the bleed passage 35 thereby determining the pressure in the crank chamber 16. In response to variation of the pressure in the crank chamber 16, a pressure differential between the pressure in the crank chamber 16 and the pressure in the compression chambers 27 though the pistons 26 is changed to vary the inclination angle of the swash plate 23, with the result of adjusted stroke of the pistons 26 or adjusted displacement of the compressor 10.

The bypass structure for residual gas in the compressor 10 will now be described.

As shown in FIG. 2, the cylinder block 11 forms therein an accommodating hole 39 that extends through the central portion of the cylinder block 11 so as to be surrounded by a plurality of the cylinder bores 25. The accommodating hole 39 partially accommodates therein the rear end portion 38 of the drive shaft 17 so as to be slidable. The rear end portion 38 of the drive shaft 17 is rotatably supported by the cylinder block 11 such that an outer peripheral surface 38 a of the rear end portion 38 directly slides on an inner peripheral surface 39 a of the accommodating hole 39. That is, the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 and the inner peripheral surface 39 a of the accommodating hole 39 cooperatively function as a plain bearing surface for supporting the rear end portion 38 of the drive shaft 17 to receive radial road.

It is noted that the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 is treated with coating for improving a slide-contact with the inner peripheral surface 39 a of the accommodating hole 39.

In the accommodating hole 39, a sliding member 21 and a coil spring 20 are interposed between an end surface 38 b of the rear end portion 38 of the drive shaft 17 and the front end surface of the valve port assembly 13 (strictly, the suction valve plate 13 a). The sliding member 21 slidably contacts with the end surface 38 b of the rear end portion 38 of the drive shaft 13. The coil spring 20 is interposed between the sliding member 21 and the valve port assembly 13 and urges the sliding member 21 toward the drive shaft 17. Accordingly, for example, even if compression reactive force is not generated during stop of the compressor 10, the coil spring 20 urges the drive shaft 17, that is, the lug plate 22, toward the thrust bearing 19. Thus, the coil spring 20 prevents the drive shaft 17, the lug plate 22, the swash plate 23, and the like from rattling forward and rearward in the direction of the axis L by the effect of vehicle vibration and the like.

It is noted that the end surface 38 b of the rear end portion 38 of the drive shaft 17 and the sliding member 21 are treated with coating for improving a slide-contact therebetween.

The cylinder block 11 forms therein communication holes 40 that connect the compression chambers 27 to the rear end portion 38 of the drive shaft 17. These plural communication holes 40 (six in the first preferred embodiment) are radially formed in the cylinder block 11 about the axis L of the drive shaft 17. One end of each communication hole 40 is opened at the inner peripheral surface of the cylinder bore 25 near the valve port assembly 13, which is an opening 40 a. Accordingly, even if the piston 26 is positioned either at the top dead center or at the bottom dead center, each communication hole 40 is in communication with the corresponding compression chamber 27. The other end of each communication hole 40 is opened at the inner peripheral surface 39 a of the accommodating hole 39 so as to face the outer peripheral surface 48 a of the rear end portion 38 of the drive shaft 17, which is an opening 40 b.

FIG. 3 is a linearly expanded plan view illustrating the rotational motion of the rear end portion 38 of the drive shaft 17 while the rotation of a certain point on the outer peripheral surface 38 a of the rear end portion 38 around the axis L is converted to leftward movement according to the first preferred embodiment of the present invention. As shown in FIG. 3, the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 forms therein a residual gas bypass groove or a residual gas bypass passage 41. The residual gas bypass groove 41 includes a high-pressure side groove 41 a, which extends in the direction along the axis L of the drive shaft 17 (or the vertical direction in FIG. 3), a low-pressure side groove 41 b, which extends in the direction along the axis L, and a connecting groove 41 c, which extends in the circumferential direction of the drive shaft 17 (or the horizontal direction in FIG. 3) to connect the front end portion of the groove 41 a to the front end portion of the groove 41 b.

The high-pressure side groove 41 a is located on the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 to face the compression chamber 27A in which the piston 26 is positioned at the top dead center, that is, the opening 40 b of the communication hole 40A that communicates with the high-pressure side compression chamber 27A that has just finished discharge process. The low-pressure side groove 41 b is located on the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 to face the compression chamber 27B in which the piston 26 is positioned at he bottom dead center, that is, the opening 40B that communicates with the low-pressure side compression chamber 27B that has just finished suction cycle. Also, the connecting groove 41 c is located on the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 so as not to face the opening 40 b of the communication hole 40.

Accordingly, refrigerant gas (residual gas), which remains due to an incomplete discharge in the compression chamber 27A that has just finished discharge process is collected into the compression chamber 27B through the communication hole 40A, the residual gas bypass groove 41 (the high-pressure side groove 41 a, the connecting groove 41 c and the low-pressure groove 41 b), and connecting hole 40B, in this order. Thus, residual gas in the compression chamber 27 during a suction process substantially does not expand, and may increase the amount of refrigerant gas introduced into the compression chamber 27, with the result of improved suction efficiency of refrigerant gas to the compression chamber 27.

According to the first preferred embodiment, the following advantageous effects are obtained.

(1) Since the rear end portion 37 of the drive shaft 17 slides in the accommodating hole 39, that is, since the rear end portion 38 of the drive shaft 17 is slidably received by the accommodating hole 39, a bearing, which is conventionally required for supporting the rear end portion 38 of the drive shaft 17, was omitted. Accordingly, the structure of the compressor 10 is simplified, and manufacturing cost is reduced.

(2) The residual gas bypass groove 41 is formed in the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17. That is, the residual gas bypass groove 41 is directly formed on the drive shaft 17. Accordingly, in comparison to a structure in which the residual gas bypass groove 41 is formed in the outer peripheral surface of a rotor that is prepared separately from the drive shaft 17 so as to synchronously rotate therewith, the number of components may be reduced and an assembling process may be omitted.

(3) The residual gas bypass groove 41 supplies residual gas in the compression chamber 27A to the compression chamber 27B that has just finished suction process. Accordingly, residual gas may further be fed from the compression chamber 27A that has just finished discharge process to the compression chamber 27B that has just finished suction process. Thus, the amount of refrigerant gas introduced into the compression chamber 27 is increased, and the suction efficiency of refrigerant gas to the compression chamber 27 is further improved.

(4) The residual gas bypass passage is substantiated as the residual gas bypass groove 41, which is formed in the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17. Accordingly, lubricating oil (refrigerating machine oil) contained in refrigerant gas that moves in the residual gas bypass groove 41 remains between the residual gas bypass groove 41 and the inner peripheral surface 39 a of the accommodating hole 39, thereby improving slide-contact between the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 and the inner peripheral surface 39 a of the accommodating hole 39. Particularly, in the first preferred embodiment, the residual gas bypass passage is formed only by a groove (the residual gas bypass groove 41), so that the slide-contact may further be improved.

The present invention is not limited to the embodiment described above but may be modified into the following alternative embodiments.

In the first preferred embodiment, the residual gas bypass passage is formed by a groove (the residual gas bypass groove 41), which is formed in the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17. In a second preferred embodiment, as shown in FIG. 4, in the rear end portion 38 of the drive shaft 17 forms therein a hole 51 that extends radially (in the direction that intersects with the axis L), and the hole 51 may be used as a residual gas bypass passage. In this case, a first opening 51 a of the hole 51 is located on the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 to face the opening 40 b of the communication hole 40A that communicates with the compression chamber 27A in which the piston 26 is positioned at the top dead center. A second opening 51 b of the hole 51 is located on the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17 to face the opening 40 b of the communication hole 40B that communicates with the compression chamber 27B in which the piston 26 is positioned at the bottom dead center.

According to the second preferred embodiment, the same advantageous effect mentioned in paragraph (4) in the first preferred embodiment is obtained. Additionally, the residual gas bypass passage is formed by the hole 51 that radially extends through the drive shaft 17. Generally, manufacturing of holes is easier than manufacturing of grooves, and, according to the second preferred embodiment, the drive shaft 17 is easily manufactured to form the residual gas bypass passage. Particularly, in the second preferred embodiment, the residual gas bypass passage is wholly formed only by the hole 51, so that the residual gas bypass passage is further easily manufactured.

In the first preferred embodiment, the residual gas bypass passage is wholly formed by a groove (the residual gas bypass groove 41). In addition, in the second preferred embodiment, the residual gas bypass passage is wholly formed by the hole 51. In a third preferred embodiment as shown in FIGS. 5 and 6, the residual gas bypass passage partially includes grooves 41A, 41B that are formed in the outer peripheral surface 38 a of the rear end portion 38 of the drive shaft 17, and the remainder of the residual gas bypass passage is formed by a hole 51A that radially extends through the rear end portion 38 of the drive shaft 17.

In the first and second preferred embodiments, the residual gas bypass passage is formed to connect the compression chamber 27A, in which the piston 26 is positioned at the top dead center, to the compression chamber 27B, in which the piston 26 is positioned at the bottom dead center. In an alternative embodiment, the residual gas bypass passage is formed to connect the compression chamber 27A, in which the piston 26 is positioned at the top dead center, to the compression chamber 27, in which the piston 26 is on the way from the top dead center to the bottom dead center (during the suction process), or to the compression chamber 27, in which the piston 26 is on the way from the bottom dead center to the top dead center (during the discharge process).

In the first and second preferred embodiments, the compressor 10 includes the even-numbered cylinder bores 25. In an alternative embodiment, the present invention is applied to a compressor that includes the odd-numbered cylinder bores 25. In this case, the residual gas bypass passage connects the compression chamber 27, in which the piston 26 is positioned at the top dead center, to the compression chamber 27, in which the piston 26 is positioned at the bottom dead center.

In an alternative embodiment, the high-pressure side compression chamber 27A, which is to supply residual gas, may employ a compression chamber, in which the piston 26 is positioned slightly offset forward or rearward to the top dead center.

In an alternative embodiment, the present invention is applied to a fixed displacement piston type compressor.

In an alternative embodiment, the present invention is applied to a double-headed piston type compressor. In this case, the present invention may be applied to both a set of front cylinder bores and a set of rear cylinder bores, or may be applied to one of the set of front cylinder bores and the set of rear cylinder bores.

In an alternative embodiment, the present invention is applied to a wobble plate piston type compressor.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

1. A piston type compressor comprising: a housing includes a cylinder block that forms a plurality of cylinder bores and an accommodating hole at a center thereof; a valve port assembly connected to the cylinder block, the valve port assembly including suction ports, suction valves made of flapper valves, discharge ports, and discharge valves made of flapper valves; a drive shaft rotatably supported by the housing and surrounded by the cylinder bores, an end portion of the drive shaft being slidably accommodated in the accommodating hole; and a piston accommodated in each of the cylinder bores, the piston and the valve port assembly forming a compression chamber, wherein the cylinder block forms therein communication holes that connect each of the compression chambers to the end portion of the drive shaft, the end portion of the drive shaft forming therein a residual gas bypass passage, wherein the residual gas bypass passage connects one communication hole, which communicates with the compression chamber on a high-pressure side that has finished discharge process of gas, to another communication hole, which communicates with the compression chamber that is lower in pressure than the high-pressure side compression chamber, and wherein as the piston reciprocates, gas being introduced into the compression chamber through the suction port by pushing away the suction valve, compressed in the compression chamber and discharged from the compression chamber through the discharge port by pushing away the discharge valve.
 2. The piston type compressor according to claim 1, wherein the residual gas bypass passage at least partially includes a groove that is formed in an outer peripheral surface of the end portion of the drive shaft sliding on an inner peripheral surface of the accommodating hole.
 3. The piston type compressor according to claim 2, wherein the residual gas bypass passage is wholly formed by the groove.
 4. The piston type compressor according to claim 1, wherein the residual gas bypass passage at least partially includes a groove that extends in a direction along an axis of the drive shaft.
 5. The piston type compressor according to claim 1, wherein the residual gas bypass passage at least partially includes a hole that radially extends through the drive shaft.
 6. The piston type compressor according to claim 5, wherein the residual gas bypass passage is wholly formed by the hole.
 7. The piston type compressor according to claim 1, wherein the residual gas bypass passage includes: a groove formed in an outer peripheral surface of the end portion of the drive shaft sliding on an inner peripheral surface of the accommodating hole; and a hole radially extending through the drive shaft.
 8. The piston type compressor according to claim 1, wherein the compressor includes the even-numbered cylinder bores.
 9. The piston type compressor according to claim 8, wherein the compressor includes six cylinder bores.
 10. The piston type compressor according to claim 1, wherein the compressor is a variable displacement type.
 11. The piston type compressor according to claim 1, wherein the piston is a single-headed type. 